Preparation of crystalline antimony sulfide



PREPARATION OF CRYSTALLINE ANTINIONY SULFIDE Willard S. Bandy, North Massapequa, N. Y., assignor to Barium and Chemicals, Eno, Willoughhy, Ghio, a corporation of Ohio N Drawing. Application June 3, 1955 Serial No. 513,160

6 Claims. (Cl. 23-136) This invention in general relates to the production of crystalline antimony sulfide, usually known as stibnite, and particularly to the production of crystalline antimony sulfide from antimony and sulfur.

The object of the present invention is to provide a novel and improved method of producing antimony sulfide directly from free antimony metal.

Another object of the invention is to provide antimony sulfide which is particularly low in arsenic content.

A further object of the invention is to provide a method by which a very rapid, nearly instantaneous reaction can be secured between particles of antimony metal and sulfur to obtain maximum combination of these materials during the processing of a mixture thereof.

Another object of the invention is to make antimony sulfide, from ground antimony metal at least 60% of which will pass through a U. S. standard 325 mesh screen, and to control removal of arsenic by the particle size of the material processed, and by the ratio of sulfur to antimony.

The foregoing and other objects and advantages of the invention will be made more apparent as the specification proceeds.

The present invention in more detail comprises grinding antimony metal in a conventional type of a grinder for producing a very small particle size of ground antimony. For example, the antimony to be processed in accordance with the invention preferably is ground of sufficient degree of fineness that at least 60% of the antimony would pass through a U. S. standard 325 mesh screen. Sulfur is thoroughly mixed with the metal as by a blender, and the mix is rapidly heated to obtain an almost instantaneous reaction and combination of the antimony and sulfur to produce antimony sulfide of the stibnite variety, which product is obtained by casting the product in a suitable mold or container.

Example In one instance, 45 pounds of sulfur in a fine state of commutation, such that 100% would pass through a U. S. standard 50 mesh screen, was sifted into the blender to break up any lumps and is thoroughly mixed with 65 pounds of antimony metal ground so that at least 60% will pass through the U. S. standard 325 mesh screen. An empty crucible was placed in a small furnace and heated, as by a gas or oil flame, until the interior of the crucible is of a uniform red-orange glow and is at a temperature of approximately 750 degrees Centigrade. Thereafter the heat is turned off and about 45 pounds of the metal-sulfur mix was added to the crucible. Upon contact with the heated crucible, an immediate reaction between the antimony and sulfur is initiated, and sulfur flames leap up from the crucible approximately six to eight feet. These flames have a red center cloud-of gaseous sulfur and sulfur burns with a bluish flame at the edges of the cloud. After approximately one to two minutes, a second container of about 45 pounds of the sulfur-metal mix is emptied into the crucible through the flames. After the mixed material is placed in the crucible, which is inert to the reaction occuring therein, the reaction is allowed to continue until the flames fall to Within about one foot of the crucible top. The furnace heat is then reapplied for approximately one half hour to forty five minutes. During such time the furnace flames preferably substantially completely surround and encompass the crucible and the heating is continued until sulfur is no longer noted visually as being evolved from the melt. That is, the flames are sporadic and two to three inches in length and approximately one quarter inch wide, which flame size is taken to indicate a substantial completion of the reaction. Prolonged heating diminishes the test for sulfide sulfur and is undesired. If not heated long enough, a gassy, honeycombed mass containing appreciable amounts of elemental sulfur is obtained. Next the melt is poured slowly into a cast iron or other suitable pot or mold and allowed to solidify. In this example of the invention, an end product of crystalline antimony sulfide was secured which contained approximately 25% sulfide sulfur of commercial quality, and the balance is primarily free antimony. A second heating of the product with additional free sulfur as described in my co-pending application Serial Number 513,159 will increase the sulfide sulfur to a total of 27.5 to 28%.

In other practice of the invention, when some larger particles of antimony have been used in the practice of the invention, the east end product has had two definite layers therein, thelower layer of which is essentially unreacted antimony metal.

Inasmuch as the flames of burning sulfur are not very hot, a workman is not subjected to any severe temperature in even manually emptying the mixed batches into the crucible. Initially the crucible may have been substantially filled with the first material placed therein but such material rapidly reduces in volume as the reaction between the sulfur and metal occurs and the mixture becomes molten. Other increments of the sulfur antimony mix may be added, as desired, when the mix has reacted sufliciently to provide available space in the crucible.

Preferably the pouring of the melt into the pot or mold of a batch of the size stated should take approximately five minutes so that any excess sulfur present in the melt is permitted to burn or boil off from the remainder of the product.

Whereusing a starting metal which had 50% of its particles pass through a 325 mesh screen, on processing by the invention, it gave approximately five pounds of regulus metal in one layer of a pound ingot and had a sulfide sulfur content in the second layer and remainder of the ingot of approximately 22%. If less sulfur than specified above is used, lower sulfide yields result, and a greater amount of regulus metal is obtained.

One special feature of the present invention is that in the regulus metal secured by employing less sulfur than specified above, some arsenic is removed and, if the starting antimony had, for example, between .07 to .08 arsenic therein, the regulus metal secured is found to have an arsenic content of approximately .02% when the stoichiometric amount of sulfur is used. If such substantially arsenic-free antimony is reground preferably to pass at least about 60% through a 325 mesh screen and processed in accordance with the invention, antimony sulfide is produced which is for all practical purposes arsenic free and has an arsenic content of less than .02%.

In practicing the invention the particle size of the sulfur is not a critical factor.

As sulfur boils at 444 degrees centigrade and has a Patented Sept. 30, 1958 Y 3. low heat of vaporization, the heat of the antimony-sulfur reaction boils ofi some sulfur from the mixture and suflicient extra sulfur over and above that theoretically combining with the antimony metal is provided to compensate for the sulfur lost because of the temperature of the reaction. The ratio of 45 pounds of sulfur to 65 pounds of antimony metal has worked well for the examples set forth. The sulfur quantity used may be varied from about 44 to 46 pounds in relation to 65 pounds of antimony when between about 50 to 60% of the antimony passes through a 325 mesh screen. Additional sulfur is not helpful. If 100% of the antimony passes through a. 325 mesh screen then as low as 40 pounds of sulfur to 65 pounds of antimony gives excellent results in the production of the desired antimony sulfide (Sb S When working to obtain antimony sulfide with low arsenic content, reducing the sulfur to 20 to 35 pounds to 65 pounds of antimony will aid in securing the desired multi-layer cast end product in which the regulus metal is low in arsenic. Normally only small quantities of low arsenic antimony sulfides are desired. The antimony sulfide upper layer concurrently produced is rather poor in sulfide content but is upgraded as described in my co-pending application referred to hereinbefore.

In view of the foregoing, it is contended that the objects of the invention have been secured and a commercial grade of stibnite has been produced.

While one complete embodiment of the invention has been disclosed herein, it will be appreciated that modification of this particular embodiment of the invention may be resorted to without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. That method of producing antimony sulfide comprising grinding antimony containing some arsenic into small particles, thoroughly mixing sulfur particles with antimony in the ratio of between about 20 to 45 pounds of sulfur to 65 pounds of antimony, heating a container to a temperature of about 750 degrees centigrade, adding the metal sulfur mixture by increments to the container, heating the container and mixture when the flame from the mixture is down to within about one foot of the container and continuing the heating until substantially no sulfur flames come from the container, slowly casting the resultant liquid to provide a solid with a layer of antimony sulfide therein and having a definite separation line therein with metallic antimony being the primary ingredient of the lower of the cast layers, said metallic antimony containing materially less arsenic than the starting antimony, grinding said metallic antimony so that at least 50% of it will pass through a 325 mesh screen, and reprocessing the ground antimony with sulfur to obtain low arsenic antimony sulfide.

2. That method of producing antimony sulfide comprising grinding antimony containing some arsenic into particles about 50% of which pass through a 325 mesh screen, thoroughly mixing sulfur particles with antimony in the ratio of 20 to 45 pounds of sulfur by the above heating, adding, heating and casting steps to 65 pounds of antimony, heating a container to a temperature of about 750 degrees centigrade, adding the metal-sulfur mixture to the container, heating the container and mixture when the flame from the mixture is down to within about one foot of the container and continuing the heating until substantially no sulfur flames come from the container, slowly casting the resultant liquid to provide a solid with a layer of antimony sulfide therein and having a definite separation line therein with metallic antimony being the primary ingredient of the lower of the cast layers, said metallic antimony containing less arsenic than the starting antimony, grinding said metallic antimony into small particles and reprocessing the ground antimony with sulfur to obtain low arsenic content antimony sulfide.

3. That method of producing antimony sulfide comprising grinding antimony to particles over 50% of which will pass through a mesh screen with 325 openings per linear inch, thoroughly mixing sulfur particles with antimony in the ratio of 40 to 46 pounds of sulfur to 65 pounds of antimony, heating a container to a temperature of about 750 degrees centigrade, adding the metalsulfur mixture by increments to the container, heating the container and mixture when the flame from the mixture is down to within about one foot of the container and continuing the heating until sulfur flames no longer rise from the container, and slowly casting the resultant liquid to provide a solid with large quantities of sulfide sulfur therein.

4. That method of producing antimony sulfide comprising grinding antimony to particles over 50% of which pass through a mesh screen with 325 openings per linear inch, thoroughly mixing sulfur particles with antimony in the ratio of about pounds of sulfur to 65 pounds of antimony, heating a container to a temperature of about 750 degrees centigrade, adding the metal-sulfur mixture to the container, heating the container and mixture when the flame from the mixture is down to within about one foot of the container and continuing the heating until sulfur flames no longer rise from the container, and cooling the resultant liquid to provide a solid with large quantities of antimony sulfide therein.

5. That method of producing antimony sulfide comprising grinding antimony into particles about of which pass through a 325 mesh screen, thoroughly mixing sulfur particles with antimony in the ratio of 20 to 45 pounds of sulfur to pounds of antimony, heatingthe metal-sulfur mixture to a temperature of about 750 degrees centigrade until reaction between the antimony and sulfur is started and flames rise several feet above the mixture, additionally heating the mixture when the flames from the mixture are down to within about one foot of the mixture and continuing the heating until substantially no sulfur flames come from the material being processed, slowly casting the resultant liquid to provide a solid with a layer of antimony sulfide therein and having a definite separation line therein with metallic antimony being the primary ingredient of the lower of the cast layers, said metallic antimony containing less arsenic than the starting antimony, grinding said metallic antimony into small particles where about 50 percent of the antimony particles pass through a 325 mesh screen, and reprocessing the ground antimony with sulfur by the heating and casting steps to obtain low arsenic content antimony sulfide.

6. That method of producing antimony sulfide comprising grinding antimony into particles about 50% of which pass through a 325 mesh screen, thoroughly mixing sulfur particles with antimony in the ratio of 20 to 45 pounds of sulfur to 65 pounds of antimony, lieating the metal-sulfur mixture to a temperature of about 750 degrees centigrade until reaction between the antimony and sulfur is started and flames rise several feet above the mixture, additionally heating the mixture when the flames from the mixture are down to within about one foot of the mixture and continuing the heating until substantially no sulfur flames come from the material being processed, and slowly casting the resultant liquid to provide a solid with a layer of antimony sulfide therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,887,920 Burns Nov. 15, 1932 OTHER REFERENCES Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 9, page 514, 2nd paragraph. Gmelin-Kraut: Handbuch der anorganischen Chemie,

Band III, Abteilung 2, Heidelberg 1908, page 701, top

of page. 

1. THAT METHOD OF PRODUCING ANTIMONY SULFIDE COMPRISING GRINDING ANTIMONY CONTAINING SOME ARSENIC INTO SMALL PARTICLES, THOROUGHLY MIXING SULFUR PARTICLES WITH ANTIMONY IN THE RATIO OF BETWEEN ABOUT 20 TO 45 POUNDS OF SULFUR TO 65 POUNDS OF ANTIMONY, HEATING A CONTAINER TO A TEMPERATURE OF ABOUT 750 DEGREES CENTIGRADE, ADDING THE METAL SULFUR MIXTURE BY INCREMENTS TO THE CONTAINER, HEATING THE CONTAINER AND MIXTURE WHEN THE FLAME FROM THE MIXTURE IS DOWN TO WITHIN ABOUT ONE FOOT OF THE CONTAINER AND CONTINUING THE HEATING UNTIL SUBSTANTIALLY NO SULFUR FLAMES COME FROM THE CONTAINER, SLOWLY CASTING THE RESULTANT LIQUID TO PROVIDE A SOLID WITH A LAYER OF ANTIMONY SULFIDE THEREIN AND HAVING A DEFINITE SEPARATION LINE THEREIN WITH METALLIC ANTIMONY BEING THE PRIMARY INGREDIENT OF THE LOWER OF THE CAST LAYERS, SAID METALLIC ANTIMONY CONTAINING MATERIALLY LESS ARSENIC THAN THE STARTING ANTIMONY, GRINDING SAID METALLIC ANTIMONY SO THAT AT LEAST 50% OF IT WILL PASS THROUGH A 325 MESH SCREEN, AND REPROCESSING THE GROUND ANTIMONY WITH SULFUR TO OBTAIN LOW ARSENIC ANTIMONY SULFIDE. 